The present invention relates to an enclosure or housing or the like for accommodating a liquid jet cutting tool which is actually fastened to the inside of the enclosure for operation while the enclosure or housing is provided with openings for the passage of work pieces, the openings being situated in two different at least essentially vertical wall portions of the enclosure or housing arranged for facing each other.
The German petty patent--utility model 8506331 suggests a liquid beam or jet cutting tool which directs a jet of high pressure on the work piece to be cut. Such a tool broadly finds utility in the motor vehicle industry e.g. for working of instrument panels, cooling grids, roof covers, floor covers or the like, from raw sheet stock. This liquid cutting technique replaces previously practiced methods using solid tool cutters as well as punching.
The aforementioned petty patent and utility model shows also a housing for the liquid jet tool which is closed on all sides except for openings to introduce as well as to extract pieces to be worked. The housing is constructed such that it has a roof portion from which the cutting tool is suspended, and the tool itself is directed through remote control.
The petty patent and utility model is of the kind that is directed to configuration aspects and it is therefore not surprising that it does not refer to any material from which this enclosure or casing is made. This lack of information as far as the particular field is concerned poses a variety of problems which as far as the utility patent is concerned seem to have been brushed aside but have to be considered when practical considerations are made concerning the making of such a housing or enclosure.
First of all there is a strength requirement; since the tool has to be mounted and positioned and held so that the forces as they occur during jet ejecting and cutting operation can be taken up with certainty. In other words the reaction of the tool against the jet and any return reaction that results from impingement of the jet upon the solid object produces forces which have to be taken up by the housing, at least that part of the housing on which the tool is mounted; but not only that, these forces must not set the tool and the housing into some kind of oscillation or vibratory motion. This is a severe problem which is almost automatically encountered owing to the fact that one of the mechanical force acting--reacting components is a liquid. Still, in order to provide for adequate cutting the cutting process must not result in the setting up of vibrations of the tool holding facility, that is the housing or enclosure or any part thereof.
Another seemingly trivial but in reality very significant problem is that the entire procedure of cutting process by means of a jet is a very noisy one. This noise cannot be tolerated and has to be attenuated. Another point is this; owing to the fact that water is seemingly a very economical media as a jet cutter, it is clear that all these various parts including a housing and so forth have to be corrosionproof whereby it should be realized that not only is water by itself a corroding substance, but the operation of liquid under very high pressure in the dynamic sense of the jet are all aspects contributing to corrosion and erosion of whatever is being hit.
A still further factor which is to be considered at this juncture is to be seen in fact that the process of a high speed water jet hitting something, anything, results in the inherent generation of a fog which again has certain corroding effects. Still another problem arises from the point that the wall of the enclosure or housing must in effect be very thick. By some accident it may be that a jet is redirected or better misdirected and rather than hitting the workpiece it hits the housing wall. Now obviously this should not provide a cutting action into the housing. The added proviso that such an accident must not only not destroy the housing is motivated by the following. If for some fluke or accident the jet does hit the housing and e.g. cuts a hole into the housing wall, people on the outside who happen to be in the vicinity could in fact be severely injured, and of course other objects that happen to be in the direction of emerging beam can be damaged too.
It can thus be seen that the making of such an enclosure and housing for a liquid jet cutting tool is not a trivial task. The seemingly obvious way of solving this problem is to construct a housing and enclosure of thick steel walls and in fact this approach has been offered. But that is not the answer. First of all, a regular steel housing is inherently quite elastic. A steel housing offers advantages; but on the other hand s steel housing is prone to undergo vibrations; such housing can even set them up vibrations for any reason. Hence the kind of vibrations and oscillations that may occur or for which there may be a tendency to set up such vibration, have to be suppressed. In fact it seems necessary to include stiffening ribs of a variety and complex matter in order to avoid that the steel housing is set into a vibratory motion.
Owing to the forces that arise these structures have to be very strongly dimensioned in order to be effective at all. Also of course the housing and enclosure including the stiffening structure has to be of some kind of closed configuration. This then leads to an inherently large amount of material that goes in the making of such a housing and enclosure. The corrosion problem outlined above could be counteracted e.g. through zinc plating. But now one encounters the problem that such a plating, though in effect a good corrosion proofing layer, is very sensitive against a kind of residual pressure of the jet. In particular, if that layer is (accidentally) hit directly by a jet it is immediately destroyed. Hence one has to include deflection sheets to avoid this possibility. These sheets may be made of steel, but if they are zinc plated, then the same problem arises; they will be subject to corrosion and little is gained. As far as the steel housing is concerned, it is of course by and in itself not a sound insulator. Therefore in order to provide the sound proofing alluded to above one will need a particular cover, lining, filling of cavities and so forth to be included in the construction of the housing and enclosure in order to provide the requisite sound attenuation. Now here again one faces the problem of corrosion. As far as this lining is concerned, there is always the problem, what happens if a misdirected jet cuts a hole into the housing at some totally unforseen location and ejects a jet towards the outside in a completely unforseeable direction and time. This is simply a problem that has not been taken care of by the various concepts concerning other problems. Obviously one answer would be to make the housing thicker and thicker and thus heavier and more expensive which is a rather primitive, unimaginative and undesirable solution.